Interface buffer layer of gradient energy band structure and preparation method thereof, and perovskite-silicon laminated solar cell

Abstract

The application discloses an interface buffer layer of a gradient energy band structure and a preparation method thereof and a perovskite-silicon laminated solar cell, and belongs to the technical field of perovskite solar cells. The interface buffer layer is arranged between an electron transport layer and a perovskite light absorption layer, and is a combination of inorganic materials and organic materials. From the side close to the perovskite light absorption layer to the side close to the electron transport layer, the volume fraction of the inorganic materials continuously increases, and the volume fraction of the organic materials continuously decreases. The application forms an 'energy slide' effect by constructing a continuous gradient change of components and energy bands, realizes superfast and barrier-free extraction of carriers, simultaneously reduces interface carrier aggregation through smooth energy band transition, suppresses non-radiative recombination and photo-induced phase separation, and effectively blocks metal ion diffusion through a dense inorganic network. The perovskite-silicon laminated solar cell based on the interface buffer layer has a significantly improved open-circuit voltage and a fill factor, and exhibits excellent illumination stability.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell technology, specifically relating to an interface buffer layer with a gradient band structure and its preparation method, and a perovskite-silicon tandem solar cell containing the interface buffer layer. Background Technology

[0002] Wide bandgap perovskites (bandgap Eg>1.65 eV, such as FA) 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3) is the key to constructing high-efficiency perovskite / silicon tandem solar cells. However, wide-bandgap perovskite solar cells, especially their interface with the electron transport layer, face many challenges:

[0003] Severe interfacial recombination and extraction barriers: Due to the imperfect band arrangement, there is often a significant conduction band or valence band shift at the interface between the perovskite and the electron transport layer, forming a barrier to carrier extraction, resulting in open-circuit voltage (Voc) loss and a decrease in fill factor (FF), accompanied by significant current-voltage (JV) test hysteresis.

[0004] Photoinduced phase separation is exacerbated: the interface is usually a defect-rich region, and under the influence of light and electric field, it not only accelerates the separation of halide ions (I₂O₃) but also... - / Br - The migration of these phases can induce more severe photo-induced phase separation and may also lead to interface degradation, becoming the starting point for device performance degradation.

[0005] Ion interdiffusion problem: Metal ions (such as TiO2, SnO2, NiOx) in commonly used metal oxide electron transport layers (e.g., TiO2, SnO2, NiOx) 4+ Sn 4+ Ni² + Under device operating conditions, the energy may diffuse into the perovskite layer, disrupting the perovskite lattice, introducing deep-level defects, and severely impairing the long-term stability of the device.

[0006] Traditional interface modification strategies, such as introducing ultrathin insulating layers (e.g., LiF, Al2O3) or passivation layers made of a single material, typically only address some issues (e.g., passivation defects or adjusting work function), and the fixed band structure makes it difficult to achieve optimal carrier extraction kinetics. More importantly, they cannot construct a multifunctional interface that can actively guide carriers while simultaneously blocking the diffusion of harmful ions. Therefore, developing a novel interface layer that can fundamentally optimize the interface band structure, suppress ion diffusion, and improve stability is crucial. Summary of the Invention

[0007] This invention is based on the inventors' discoveries and understanding of the following facts and problems: the interface problem between the wide-bandgap perovskite light-absorbing layer and the electron transport layer is a key bottleneck limiting device performance and stability. In the prior art, the application of gradient bandgap structures in perovskite solar cells is mainly limited to the compositional gradient inside the perovskite light-absorbing layer or the doping gradient of the electron transport layer. A scheme using an interface buffer layer with continuously varying compositional and bandgap gradients constructed from inorganic-organic hybrid materials for wide-bandgap perovskite top solar cells is still lacking.

[0008] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose an interface buffer layer with a gradient band structure, a method for its fabrication, and a perovskite-silicon tandem solar cell.

[0009] In a first aspect, embodiments of the present invention provide an interface buffer layer with a gradient band structure, wherein the interface buffer layer is disposed between an electron transport layer and a perovskite light absorption layer, and the material of the interface buffer layer is a combination of inorganic and organic materials. From the side near the perovskite light absorption layer to the side near the electron transport layer, the volume fraction of the inorganic material in the interface buffer layer continuously increases and the volume fraction of the organic material continuously decreases.

[0010] The advantages and technical effects of the interface buffer layer in this embodiment of the invention are as follows: (1) The “slippery slope” effect promotes carrier extraction: Inorganic materials usually have a deeper conduction band bottom. The volume fraction of inorganic materials increases continuously from the perovskite light absorption layer side to the electron transport layer side, which means that the conduction band bottom energy gradually decreases from the perovskite light absorption layer side to the electron transport layer side, forming an “energy downhill” from the perovskite light absorption layer to the electron transport layer. After photogenerated electrons are injected from the perovskite light absorption layer into the interface buffer layer, they are rapidly and directionally “transported” to the external electron transport layer and electrodes under the drive of the built-in gradient field, which completely eliminates the energy barrier and carrier accumulation at the interface, significantly improves the electron extraction efficiency, reduces interface recombination, and eliminates JV hysteresis.

[0011] (2) Suppressing interfacial recombination and phase separation: The smooth band transition avoids the accumulation of charge carriers at sharp interfaces and reduces the probability of nonradiative recombination. At the same time, efficient charge extraction reduces charge accumulation at the interface and lowers the local electric field, thereby suppressing the migration of halide ions and photoinduced phase separation at the interface.

[0012] (3) Ion diffusion barrier layer: The inorganic nanocrystals enriched near the electron transport layer form a dense physical barrier, which can effectively block the diffusion of metal ions from the electron transport layer to the perovskite light absorption layer. The organic components enriched near the perovskite light absorption layer ensure the continuity of the film and good contact with the perovskite light absorption layer.

[0013] In some embodiments, the inorganic material is a metal oxide nanocrystal and / or a metal halide nanocrystal; the organic material is a conjugated polymer and / or a fullerene derivative.

[0014] In some embodiments, the inorganic material is selected from at least one of TiO2, SnO2, ZnO, WO3, PbI2, and CsPbBr3 nanocrystals.

[0015] In some embodiments, the organic material is selected from at least one of PTAA, P3HT, PCDTBT, PCBM, and ICBA.

[0016] In some embodiments, on the side near the perovskite light-absorbing layer, the volume fraction of the inorganic material in the interface buffer layer is 0% to 30%, and the volume fraction of the organic material is 70% to 100%. This side is enriched with organic polymers to provide good interfacial contact with the perovskite light-absorbing layer and reduce interface defects.

[0017] In some embodiments, on the side near the electron transport layer, the volume fraction of the inorganic material in the interface buffer layer is 70%–100%, and the volume fraction of the organic material is 0%–30%. This side is enriched with inorganic nanocrystals to provide energy level connections that match the conduction band of the electron transport layer and to form an effective ion blocking layer.

[0018] In some embodiments, the thickness of the interface buffer layer is 5–50 nm. This thickness range ensures the formation of an effective gradient band structure without significantly increasing series resistance or affecting light transmission.

[0019] Secondly, the present invention provides a method for preparing an interface buffer layer with a gradient band structure, comprising the following steps: Prepare inorganic material precursor solutions and organic material precursor solutions; The interface buffer layer is deposited on the electron transport layer using a solution gradient deposition technique. During the deposition process, the relative deposition rate of the inorganic material precursor and the organic material precursor is continuously changed, so that the volume fraction of inorganic material in the film after deposition continuously increases from the side closer to the perovskite light absorption layer to the side closer to the electron transport layer, while the volume fraction of organic material continuously decreases. The deposited film is annealed to obtain the interface buffer layer.

[0020] The advantages and technical effects of the method for preparing the interface buffer layer of the present invention are as follows: The preparation method of this invention achieves continuous gradient changes in components through solution gradient deposition technology, which does not require expensive vacuum equipment, is simple in process, is compatible with large-area coating process, and has the potential for industrial application.

[0021] In some embodiments, the solution gradient deposition technique is a dual-channel spraying method, a dual-channel blade coating method, or a stepped spin coating method. When using the dual-channel spraying method, the flow rate ratio of the two precursor solutions is changed continuously and in real time during the deposition process, thereby achieving in-situ gradient changes of components in the grown film.

[0022] Thirdly, the present invention provides a perovskite-silicon tandem solar cell, wherein the interface buffer layer described in the first aspect is disposed between the electron transport layer and the perovskite light absorption layer of the perovskite-silicon tandem solar cell.

[0023] The advantages and technical effects of the perovskite-silicon tandem solar cells of this invention are as follows: (1) Maximize carrier extraction efficiency: The gradient band structure of the interface buffer layer provides the driving force, realizing ultrafast and barrier-free extraction of carriers, greatly improving the device's fill factor (FF) and short-circuit current (Jsc), and completely eliminating the hysteresis phenomenon in current-voltage testing.

[0024] (2) Significantly improve open-circuit voltage: By reducing interfacial recombination through the interface buffer layer, the open-circuit voltage (Voc) of the device is closer to the theoretical limit of the material, which is crucial for the tandem solar cell formed by the wide-bandgap perovskite light absorption layer.

[0025] (3) Excellent light stability: The efficient charge extraction and ion blocking capabilities enable the device to exhibit extremely high power output stability under continuous irradiation with high light intensity (such as 1.5 times the sunlight or higher), and photo-induced phase separation is significantly suppressed. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] Example 1: SnO2+PCBM interface buffer layer Materials preparation: Prepare an isopropanol solution of SnO2 nanocrystals (solution A, 5 mg / mL) and a chlorobenzene solution of PCBM (solution B, 5 mg / mL).

[0028] Interfacial buffer layer preparation: A dense SnO2 layer was pre-deposited on a silicon-based solar cell. A dual-channel spraying system was used to spray solution A and solution B onto the dense SnO2 layer. Initially, the flow rate of solution A was 100%, and that of solution B was 0%. During the 10-second deposition period, the flow rates were linearly adjusted so that the flow rate of solution A was 0% and that of solution B was 100% at the end. This formed a 20 nm thick interfacial buffer layer that transitioned from SnO2-rich to PCBM-rich, followed by annealing at 80°C for 10 minutes.

[0029] Device fabrication: FA is deposited on the interface buffer layer. 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 3. Perovskite thin film. Subsequently, Spiro-OMeTAD and Au electrodes were deposited on the perovskite thin film to assemble a perovskite-silicon tandem solar cell.

[0030] Test results: The device's open-circuit voltage Voc = 1.28 V, short-circuit current density Jsc = 20.0 mA / cm², fill factor FF = 84%, photoelectric conversion efficiency PCE = 21.5%, and the JV curve shows almost no hysteresis. After 1000 hours of operation under one sun and 50°C, the MPPT retains more than 93% of its initial efficiency.

[0031] Example 2: TiO2+PCBM interface buffer layer The interface buffer layer and the stacked battery were prepared using the same method as in Example 1, except that SnO2 nanocrystals were replaced with TiO2 nanocrystals.

[0032] Test results: The device's open-circuit voltage Voc = 1.27 V, short-circuit current density Jsc = 19.9 mA / cm², fill factor FF = 83%, photoelectric conversion efficiency PCE = 21.2%, and the JV curve shows almost no hysteresis. After 1000 hours of operation under one sun and 50°C, the MPPT retains 92% of its initial efficiency.

[0033] Example 3: SnO2+ICBA interface buffer layer The interface buffer layer and the stacked battery were prepared using the same method as in Example 1, except that PCBM was replaced with ICBA.

[0034] Test results: The device's open-circuit voltage Voc = 1.26 V, short-circuit current density Jsc = 19.8 mA / cm², fill factor FF = 82.5%, photoelectric conversion efficiency PCE = 21.0%, and the JV curve shows almost no hysteresis. After 1000 hours of operation under one sun and 50°C, the MPPT retains 91% of its initial efficiency.

[0035] Example 4: The interface buffer layer and the stacked battery were prepared using the same method as in Example 1, except that at the beginning, the flow rate of liquid A was 70% and that of liquid B was 30%; during the 10-second deposition time, the flow rate was linearly adjusted so that the flow rate of liquid A was 30% and that of liquid B was 70% at the end.

[0036] Test results: The device's open-circuit voltage Voc = 1.26 V, short-circuit current density Jsc = 19.9 mA / cm², fill factor FF = 82%, photoelectric conversion efficiency PCE = 20.9%, and JV hysteresis is slight. After 1000 hours of operation under one sun and 50°C, the MPPT retains 90% of its initial efficiency.

[0037] Comparative Example 1: No interface buffer layer Perovskite films were directly deposited on dense SnO2, with other steps the same as in Example 1.

[0038] Test results: The device's open-circuit voltage Voc = 1.22 V, short-circuit current density Jsc = 19.6 mA / cm², fill factor FF = 78%, photoelectric conversion efficiency PCE = 19.5%, and significant JV hysteresis. After 1000 hours of operation under one sun and 50°C, the MPPT retains 75% of its initial efficiency.

[0039] Comparative Example 2: Interface buffer layer with homogeneous SnO2 + PCBM composition Materials preparation: Prepare an isopropanol solution of SnO2 colloidal nanocrystals (solution A, 5 mg / mL) and a chlorobenzene solution of PCBM (solution B, 5 mg / mL).

[0040] Preparation of interface buffer layer: Liquid A and liquid B are mixed in a volume ratio of 1:1 to form a homogeneous solution. The homogeneous solution is then sprayed onto the pre-deposited dense SnO2 layer for 10 minutes to form a 20 nm thick interface buffer layer of homogeneous SnO2+PCBM mixture. The layer is then annealed at 80°C for 10 minutes.

[0041] Test results: The device's open-circuit voltage Voc = 1.25 V, short-circuit current density Jsc = 19.7 mA / cm², fill factor FF = 80%, photoelectric conversion efficiency PCE = 20.2%, and JV hysteresis is slight. After 1000 hours of operation under one sun and 50°C, the MPPT retains 88% of its initial efficiency.

[0042] Comparative Example 3: Reverse Interface Buffer Layer Prepared in the same manner as in Example 1, except that the flow ratio is adjusted in the opposite direction, so that the volume fraction of inorganic material decreases from the perovskite light absorption layer side to the electron transport layer side.

[0043] Test results: The device's open-circuit voltage Voc = 1.23 V, short-circuit current density Jsc = 19.6 mA / cm², fill factor FF = 79%, photoelectric conversion efficiency PCE = 20.0%, and JV hysteresis is slight. After 1000 hours of operation under one sun and 50°C, the MPPT retains 86% of its initial efficiency.

[0044] Table 1. Performance comparison of perovskite top solar cells in each embodiment and comparative example

[0045] According to the data in Table 1, the interface buffer layer of the gradient band structure in Examples 1-3 of this invention significantly outperforms the comparative examples in terms of open-circuit voltage, fill factor, and photoelectric conversion efficiency. In particular, compared to Comparative Example 1, Example 1 shows an increase in Voc from 1.22 V to 1.28 V (an increase of 60 mV), an increase in FF from 78% to 84% (an increase of 6 percentage points), an increase in PCE absolute value from 19.5% to 21.5% (an increase of 2.0 percentage points), and a reduction in JV hysteresis from "significant" to "almost none." Examples 2 and 3 also demonstrate excellent performance improvements, proving that this gradient structure design has good universality for different inorganic materials (TiO2, SnO2) and different organic materials (ICBA, PCBM).

[0046] Comparative Example 2 uses an interface buffer layer with a uniform SnO2 + PCBM mixture. Its Voc = 1.25 V, FF = 80%, and PCE = 20.2%, while superior to Comparative Example 1 (which lacks an interface buffer layer), is still significantly lower than Example 1. Comparative Example 3 uses a reverse gradient (inorganic material volume fraction decreasing from the perovskite light absorption layer side to the electron transport layer side). Its performance is similar to Comparative Example 2, but significantly lower than Example 1. The comparison results of Comparative Examples 2 and 3 fully demonstrate that the mere presence of an inorganic / organic hybrid layer is insufficient to achieve optimal interface optimization. The gradient structure with a continuously increasing inorganic material volume fraction from the perovskite light absorption layer side to the electron transport layer side is key to forming an effective "energy downhill," eliminating extraction barriers and carrier accumulation, thereby significantly improving device performance and stability.

[0047] By comparing Example 4 and Example 1, the significant impact of the gradient variation range on performance was verified: full gradient variation (0%→100% flow) can provide the largest bandgap adjustment range, the best ion blocking effect and the best interface contact, and is the preferred solution to maximize device performance.

[0048] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An interface buffer layer with a gradient band structure, characterized in that, The interface buffer layer is disposed between the electron transport layer and the perovskite light absorption layer. The material of the interface buffer layer is a combination of inorganic and organic materials. From the side closer to the perovskite light absorption layer to the side closer to the electron transport layer, the volume fraction of the inorganic material in the interface buffer layer continuously increases and the volume fraction of the organic material continuously decreases.

2. The interface buffer layer according to claim 1, characterized in that, The inorganic material is a metal oxide nanocrystal and / or a metal halide nanocrystal; the organic material is a conjugated polymer and / or a fullerene derivative.

3. The interface buffer layer according to claim 2, characterized in that, The inorganic material is selected from at least one of TiO2, SnO2, ZnO, WO3, PbI2, and CsPbBr3 nanocrystals.

4. The interface buffer layer according to claim 2, characterized in that, The organic material is selected from at least one of PTAA, P3HT, PCDTBT, PCBM, and ICBA.

5. The interface buffer layer according to claim 1, characterized in that, On the side near the perovskite light-absorbing layer, the volume fraction of the inorganic material in the interface buffer layer is 0% to 30%, and the volume fraction of the organic material is 70% to 100%.

6. The interface buffer layer according to claim 1, characterized in that, On the side near the electron transport layer, the volume fraction of the inorganic material in the interface buffer layer is 70% to 100%, and the volume fraction of the organic material is 0% to 30%.

7. The interface buffer layer according to claim 1, characterized in that, The thickness of the interface buffer layer is 5–50 nm.

8. A method for preparing an interface buffer layer with a gradient band structure, characterized in that, The preparation method includes the following steps: Prepare inorganic material precursor solutions and organic material precursor solutions; The interface buffer layer is deposited on the electron transport layer using a solution gradient deposition technique. During the deposition process, the relative deposition rate of the inorganic material precursor and the organic material precursor is continuously changed, so that the volume fraction of inorganic material in the film after deposition continuously increases from the side closer to the perovskite light absorption layer to the side closer to the electron transport layer, while the volume fraction of organic material continuously decreases. The deposited film is annealed to obtain the interface buffer layer.

9. The preparation method according to claim 8, characterized in that, The solution gradient deposition technique is a dual-channel spraying method, a dual-channel scraping method, or a stepped spin coating method.

10. A perovskite-silicon tandem solar cell, characterized in that, The perovskite-silicon tandem solar cell has an interface transport layer as described in any one of claims 1 to 4 disposed between the electron transport layer and the perovskite light absorption layer.

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